It isn't an easy car to launch well. Requires practice. I got mine to 4.2 eventually (not sure how accurate P3 gauge is though)

Most likely I would think it's based on the same feedback from the wheels and therefore it would be as inaccurate as our speedo's are. I think the last time I compared my GPS speed to my speedo, the cruise control was set at 100kph but the GPS read about 92-93kph.